chvA Locus May Be Involved in Export of Neutral Cyclic ?-1,2-Linked D-Glucan from Agrobacterium tumefaciens. Kevin P. O’Connell. Department of Plant Pathology, University of Wisconsin, 1630 Linden Drive, Madison 53706 U.S.A. Jo Handelsman. Department of Plant Pathology, University of Wisconsin, 1630 Linden Drive, Madison 53706 U.S.A. . MPMI 2:11-16. Accepted 22 November 1988. Copyright 1989 The America Phytopathological Society.

Extracellular and intracellular neutral ?-1,2-linked d-glucan content was determined in a virulent, attachment-deficient mutants of Agrobacterium tumefaciens that map in the chvA locus. chvA mutants contained approximately the same amount of intracellular glucan as cells of the virulent control strain A759, but released into the culture medium only 2% of the glucan released by strain A759. Introduction of a cosmid carrying the wild-type chv region restored attachment and virulence and restored extracellular glucan production to chvA mutant A2505. Exogenous glucan did not enhance or inhibit attachment or tumorigenesis of the virulent control strain or the chvA or chvB mutants. Our results suggest that the chvA locus is involved in the export of glucan from the cell and that export may be required for tumorigenesis.